Continuation (on the potential diagnosis based on what ended up happening to me)....
If you started your tank off with any/all of: Live sand, bacteria starter cultures / anything that makes a reef tank “immediately fish ready” what you accomplish is just that: enough bacteria that if you’re smart about adding fish, you’ll have a culture of bacteria that can process the ammonia. This also means you’ll also have a source of ammonia that will sustain/grow the bacteria. Then we slowly add more fish, test the water parameters & pat ourselves on the back that ammonia never spikes and your fish are happy.
Success!! Except, if you’re like me (and clearly I’m not sure if this describes your situation): I never actually had any material Nitrate readings when I cycled my tank. Occasionally I’d see a bit of an ammonia spike in the early stages (which I promptly
#TypeA addressed with water changes + I’d dose a little AmGuard just in case – I hated the idea of taking care of a living thing & stressing it out, so that seemed like the right thing to do). I proceeded in that manner (periodically buying more bacteria starters, doing water changes, adding Marine Pure blocks etc etc). I ran my skimmer, used Purigen, Activated Carbon, GFO until I had crafted my perfect little ecosystem with 8 fish, some inverts (including a sea urchin named Fuzz – b/c ironic names are fun) and a variety of SPS, LPS & Anemones. All the while kind of wondering how I had ‘cracked the code’ and never really seen any appreciable level of nitrates. Not to mention my water was “pristine” (I sent off samples to ATI for the ICP analysis etc.) Everything looked great, and my fish were super happy.
So, you can imagine my surprise when my coral started bleaching (and as you said, not just the tips). Here’s where I hope it’s helpful to pause the narrative and list out some facts that became key to solving the problem:
- Pristine water conditions (0 nitrates/phosphate etc) are not actually good for coral – the zooxanthellae need to consume nitrates & phosphates (which they, in turn metabolize into amino acids that are useful to the coral).
- Conversely, too much nitrate = too much zooxanthellae (among other things) = decreased skeletogenesis + brown corals
- In addition to coloration, zooxanthellae function a bit like ‘sunscreen’ for coral
- The Zooxanthellae population is largely regulated by the amount of nutrients available (nitrates & phosphates).
- 2 Primary Sources: dissolved organics in your water column & also the coral’s own metabolic process (which generates waste that is then symbiotically used by the Zs).
- Skeletogenesis is driven largely by mineral content available (Ca, dKH etc)
- Bleaching is a result of a coral losing its Zooxanthellae population. This can happen for a variety of reasons (some key pathways are as follows):
- Corals are able to actively expel Zooxanthellae from their tissue. This tends to happen b/c there’s an overabundance in their tissue (seemingly not your issue); or, alternatively the Zooxanthellae have died of starvation (in which case, why host dead bacteria. Yuck. So coral expels the dead/worthless Zooxanthellae)
- If the Zooxanthellae have insufficient nutrients, they die. -> Coral expels dead bacteria -> Coral has no color or UV protection -> Coral bleaches (entire colony, not just the tips)
- Interestingly, when only the tips are bleaching it’s often an indicator that your water parameters are ideal for maximizing the rate of skeletogenesis (i.e. excellent Ca/Alk). In this case, a coral’s skeleton grows faster than the Zooxanthellae population and we’re left with the new-growth having inadequate ‘sunscreen.’
- Annoyingly, this situations means that one’s lights are set perfectly for coral that’s got adequate coverage of Zooxanthellae; but too high for the new-growth segments that aren’t protected from the UV exposure.
- So ideally, we match the growth rates of Zooxanthellae with that of Skeletogenesis. That way new growth happens & is protected from over-exposure to UV.
Conclusions we can derive from the above:
- Since your entire corals are bleaching (not just the tips) it means the whole population of Zooxanthellae is suffering
- Too be fair, you can ‘irradiate’ your corals with such high lighting that the entire population bleaches (not just the tips). And, while I think your lights might be too high, I think the real explanation for colony loss of Zooxanthellae is ‘starvation.’
- Since you have 0 Nitrates or Phosphates, it stands to reason you have 0 food. Sure there might be brief windows where these nutrients are present. But excellent husbandry/vigilance is highly effective at exporting DOCs before they’re even allowed to turn into nitrates (Skimmer, Resins, etc.).
- What little remains of these DOCs does briefly cycle into nitrates which is then most rapidly taken up by any amount of algae in the tank (and I’m not even talking about a ‘bloom.’) In fact, if your situation is like mine, I only ever had the most modest traces of algae – turns out it’s because I was so effective at exporting nutrients, that the algae was also ‘starved.’ It existed only in sufficient quantity to process Nitrate & Phosphates that my carefully-planned system couldn’t process itself (which was very little… because I’m crazy and obsessive about everything).
- By keeping a pristine tank from the very beginning, we actually ****** the ability to ‘finish the cycle.’ By the time we’ve added starter cultures + fish + skimmer + resins/whatever, we’ve tipped the scales to favor the bacterial cultures that convert Ammonia to Nitrite and we’ve created a highly efficient process to limit the waste that drives that cycle. The result is very happy fish & a tank that can pretty rapidly host a fair number of fish pretty early (assuming you’re vigilant).
- The problem is that it seems like the only cycle that’s really spotlighted is the Nitrate Cycle. There’s so much other (cool) stuff happening that’s also a cycle. Like when there’s a diatom bloom then red slime ‘algae’ then green algae. This cycle overlaps the Nitrate cycle (and it’s an effective way of converting the last stage of the nitrate cycle (Nitrate) to algae/plants).
- By the time we’re (accidentally) controlling Nitrates with a combination approach of Algae & Chemistry (resins/limiting DOCs to begin with), it’s virtually impossible to increase the level of nitrates available to your Zooxanthellae because the algae & your skimmer/resin are far more efficient users of those building-blocks. So you’d have to really overdose your tank in order to outpace the algae growth and feed your Zooxanthellae (which is clearly a horrible idea lol).
The suggested action-steps above actually re-tackle the process of finishing your cycle (with an attempt not to hurt your fish – which honestly was scary to me when I realized what I thought was necessary to fix the problem). Basically you have to do the opposite of everything you set out to accomplish in the first place: let your tank get ‘dirty’ – except this time you’re responsible for keeping fish alive & happy. So, I know this has been super long (if anything I hope it’s useful even if it’s overly verbose), but here are the final things that come in to play if you think the above describes your situation…
- The reason you’re turning off the lights in your fuge is to kill photosynthesis. It’s likely you’ve got some amt of algae (possibly even intentional like Chaeto). At this point all that’s doing is sucking up the food your Zooxanthellae desperately needs. So you need to cut off photosynthesis (which isn’t an option in your main tank at this point).
- At this point, if you’re fuge is total darkness & you shut off your skimmer + started feeding more, you’re going to succeed at creating more nutrients than the current system can export… and that’s going to mean you start seeing Nitrates. **Note: I’d take daily readings if you go this route. While you need nitrates for your coral to thrive, you can’t afford to let that happen too quickly or you have other problems.
- Meanwhile if you add something like Marine Pure blocks, you’ve got sufficient real-estate to host anoxic bacteria. Which means you can finish the cycle… if you’re successful at relatively starving off algae, you can re-prioritize the growth of anoxic bacteria. Which will then take over as the predominate method for converting Nitrate.
- After about a week of no skimmer, I turned it back on b/c I was about to start ‘Phase 2’…
- Red Sea’s Tank Maturity program. They claim to have a bacteria starter that includes anoxic strains too. And they have a little bottle of ‘bacteria food’ that purportedly also target feeds these anoxic strains. Score! (except that this food is toxic to fish – it’s basically all the waste that they’d create in order to naturally create the cycle). As a result, I think I used like:
- 1ml of the Bacto-Start culture (I have a Reefer 350) every other day for a week (then upped to daily for a week)
- 1ml of NoPOx daily then upped to 1ml 2x per day (important to run your skimmer)
- I doubled the dose of the NitroBac (the actual bacteria culture). And added it every day I added the Bacto-Start. This is not according to the directions, but that’s b/c I was using it with a tank that had mostly cycled & was host to fish. I had every reason to believe there was already a natural source of ‘bacto-start’ and I couldn’t risk not having enough bacteria present to process that.
- I also started by removing 50% of my Purigen/GFO – which scared me b/c I was pulling multiple levers at once:
- No fuge lights -> less algae -> more nutrients
- No Skimmer -> No nutrient export -> more nutrients
- Less Purigen/GFO -> more nutrients
- Red Sea Bacto Start -> more nutrients
- Have to admit, after writing #5, I wonder if I over-did the correction. I was a maniac about testing levels though and I was ready to do a huge water change & throw in gallons of purigen in a second’s notice if it became necessary lol.
Like Magic though – after about 2 weeks, I saw nitrates creep up. I sent off more samples to ATI just b/c I wanted an actual read-out on nitrate/phosphate levels (not just color change by my titration). The results came back with 1.73 mg/l of Nitrates and .04mg/l PO4.
Fun random fact for anyone in Manhattan… ATI lets you send in your tank water + RO/DI water. The first time I did the test, I sent in my RO/DI water, which came back with a bunch of non-exciting 0s (duh). The second go around, I thought “hum what I use this opportunity to test what everyone says about NYC tapwater and send that through as my RO/DI sample???” Well, according to ATI, I need to “Check my RO/DI unit and consider changing my DI Resin” hahah.. but it’s actually pretty true: NYC tap water isn’t so bad! If anyone’s curious I’ll post the readout J.
But, at that point I already knew the plan worked -- all my coral looked just like I’d always wanted – tons of color, excellent polyp-extension, and even the supposedly ‘fast-growing’ corals were actually ‘fast-growing’… I could see they were spilling off the plugs etc. Sometimes I felt like I could even see minor growth within a day (super minor). But the point being: the proof was in the pudding for me: my water quality was great for fish & even for skeletal growth of corals, but I stopped biology from its natural path & as a result I couldn’t keep a healthy Zooxanthellae population. By going through the above steps, I think I managed to finish the cycle and create a better ecosystem for processing nitrates, but not so perfectly that I starve the coral.
More than anything, I wish you the very best of luck and hope that some of this might have been helpful. Also, a huge thank you to everyone who posts… even though I’ve never posted before I’ve consumed so much helpful material from so many people who contribute their time and experiences in this forum!
